1. Field of the Invention
The present invention relates to supply or take-up mandrils for ribbon material in a system that requires the ribbon material to be kept taut throughout its path of travel, and more particularly pertains to new and improved take-up or supply mandrils for use in printing mechanisms having more than one printing head per machine.
2. Description of the Prior Art
In the field of multiple print head printers and specifically, high speed drum type impact printers designed for imprinting alpha-numeric characters and MICR on documents, it has been the practice to mount separate ribbon rolls on a single supply mandril in the system. One roll of ribbon would contain regular ink for alphanumeric printing. The other roll of ribbon would contain magnetic ink for the printing of the MICR code. The mandril is in a driven system designed to supply a taut ribbon across a print head. In those instances where one roll of ribbon has a greater diameter than another roll of ribbon, due to manufacturing differences or due to one roll being half used, the diameter of the two rolls vary. As a result, there will be a difference between the speed of the two ribbons. The smaller diameter ribbon roll must travel faster than the larger diameter one to dispense the same amount of ribbon. The feedback mechanism of the printer system controls the supply mandril based upon the one ribbon that is taut. The other ribbon will not be so controlled, causing it to exhibit slack across the print head. The degree of slackness will depend upon the diameter difference between the two rolls.
Any degree of slackness can not be tolerated, because it creates fuzziness in the letters being printed. The slight fuzziness which may be tolerable in alpha-numeric printing, is intolerable when MICR code is being printed. In order to overcome this critical problem, the present invention provides a split mandril mechanism that simply replaces the single mandrel of the prior art with no changes to the ribbon control system of the printer being required. The split mandril of the present invention allows the ribbon rolls mounted thereon to rotate at different speeds.